Peanut disease control much easier with good rotation

Peanut producers with better rotations have more freedom when deciding on a disease control program.
Shorter crop rotations can lead to more pressure from white mold disease.
Peanut Rx allows growers to develop prescription fungicide programs.

Whenever peanut prices are low, growers naturally begin considering where they can reduce inputs. And, since the most expensive input in peanut production is disease control, that’s the most logical place to start.

But a better crop rotation gives growers more freedom in deciding where to cut, says Austin Hagan, Auburn University Extension plant pathologist.

Growers in Alabama’s Wiregrass region in the southeast portion of the state have seen quite a bit of pressure from white mold disease in recent years, says Hagan.

“This is particularly true in early planted peanuts – you have a higher risk of white mold if you plant in April than you do if you plant in mid-May. Once you’re into the third week of May, the risk of white mold almost drops out of the equation,” he says.

If you planted in mid-April and you’re going into a field with a history of white mold problems, you might want to look at an early season over-the-top banded application of a material like Convoy, Proline or Abound, he says.

In one trial, one application of Convoy at 40 days did as well as a multi-application program, he says. “This is a treatment that you might want to look at only if you’re planting early in a field with a history of the disease,” he says.

The good news for peanut producers, says Hagan, is that there’s an abundance of peanut fungicides on the market today.

“The products we’ve looked at in our trials all do a very good job. We have products that are specific only for leafspot. And if you’re in a situation with a good rotation, then that might well be the direction in which you should go rather than worry too much about soil-borne diseases. If you’ve had peanuts in a field for two to four consecutive years, that probably would be a good time to think about putting a white mold material in your program.”

Name-brand products, of course, tend to cost more than generics, says Hagan, but they tend to give better yield results. “But if you have a field with low disease pressure, you can do a good job with some of these generic materials,” he says.

Peanut Rx is a rules-based system that allows growers to develop a prescription-based program for each field on a farm, says Hagan.

“You don’t have to make seven fungicide applications if you’re in a good rotation situation. Planting the right variety in the right row spacing and the right situations will allow you some leeway in disease control.

“Peanut Rx allows you to determine if you can get by with five or even a four-spray program. Major companies are participating in this program so that you can follow these recommendations and not void the warranty on the materials you’re applying.”

Money savings add up

With most of the Peanut Rx recommendations, growers are keeping the core of a white mold program and adding or deleting leafspot sprays such as chlorothalonil. “You can save from $5 to $7 per application, and that adds up when you’re able to cut out one to three applications. With those additional chlorothalonil applications, you might be buying a little insurance.”

One of the issues with Peanut Rx is that growers could see increases in leafspot, says Hagan. “So you need to be cognizant of that if you get into a wet weather pattern, or if a tropical storm is coming. If it has been 10 days since you’ve put out a leafspot fungicide, you might want to spray in front of a tropical storm. If it has been three or four days before the storm since you’ve made an application, you’re probably in the clear. But if it has been from seven to 14 days, it’s best to get out in front of it.”

Peanut Rx is especially advantageous with new cultivars such as Georgia-06G, says Hagan. “Improved cultivars like Georgia-06G don’t lose a lot of yield as the leaves are lost to defoliation. With older varieties like Florunner, if you lost 25 to 40 percent of the leaves, then you lost 25 to 40 percent of the yield. With a variety like Georgia-06G, you don’t actually start to see the yields decrease regardless of the amount of defoliation until you get a least 70-percent defoliation. This allows you some margin of error in this type of program.”

New fungicides are on the market this year and there could be others before season’s end, says Hagan. “Fontelis from DuPont came out last year, and it has done a good job in our trials. It’s a premium leafspot/white mold material. Topguard is a triazole fungicide that’s probably similar to the old tebuconizoles, and it’s used basically in the same way, and it performs as good as or better than the old generic tebuconozoles. Priaxor is a new product from BASF and one that we’re just starting to get a look at.”

If you planted peanuts early, you definitely will have less leafspot in the field, says Hagan.

“And on the Gulf Coast, you have less risk of rust because the peanut matures before the rust moves in. But there is more risk of white mold. And if tomato spotted wilt virus ever comes back, it’ll come back with both feet on April-planted peanuts. On the flip side, the later you go, the more leafspot you’ll have because the disease will build up on the early peanuts and move on to the later ones. There will be less white mold because the peanuts will mature in September. From a disease standpoint, there are pluses and minuses in planting early. On the production side, there are more advantages than disadvantages in planting early.”